Charging or not ?

Hi all,

Well I am not a real hardware expert (i know my way around but thats it). My car has some problems charging its battery and I just want to see if its charging. I added a nice voltage meter to my car and I can see how much voltage my battery is producing. I want to have a light that turns on when my voltage is over 13V (because if it is it is charging else its only draining ). So how would I do this is there some sort of relay available or what.

I think the best way to be able to do what you want would be to hook up an ammeter between the battery and the car (it would have to be a really high rated ammeter though). This way (if the in was connected to the battery and the out was connected to the car) the ammeter would show positive current if the battery was being discharged, and negative current if it was being charged.